The following program crashes javac. This crash can reproduced with all versions of javac up to Java 8 (when support for lambdas was introduced).

class Outer { // bug
    interface A { }

    class Inner {
       Inner() {
          this(() -> {
             class Local {
                void g() {
                   m();
                }
             }
             new Object() {
                void k() { new Local().g(); }
             }.k();
          });
       }
      
       Inner(Runnable tr) {
          tr.run();
       }
    }

    void m() {
       System.out.println("Hello");
    }

    public static void main(String[] args) {
       new Outer().new Inner();
    }
}

Output:
n exception has occurred in the compiler (22). Please file a bug against the Java compiler via the Java bug reporting page (https://bugreport.java.com) after checking the Bug Database (https://bugs.java.com) for duplicates. Include your program, the following diagnostic, and the parameters passed to the Java compiler in your report. Thank you.
java.lang.AssertionError
at jdk.compiler/com.sun.tools.javac.util.Assert.error(Assert.java:155)
at jdk.compiler/com.sun.tools.javac.util.Assert.check(Assert.java:46)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor$LambdaTranslationContext.addSymbol(LambdaToMethod.java:2123)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.visitClassDef(LambdaToMethod.java:1347)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:814)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:70)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitBlock(TreeTranslator.java:167)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.visitBlock(LambdaToMethod.java:1312)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1092)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitLambda(TreeTranslator.java:306)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.analyzeLambda(LambdaToMethod.java:1428)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.visitLambda(LambdaToMethod.java:1406)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCLambda.accept(JCTree.java:1993)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:70)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitApply(TreeTranslator.java:292)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.visitApply(LambdaToMethod.java:1289)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1816)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitExec(TreeTranslator.java:257)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1603)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:70)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitBlock(TreeTranslator.java:167)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.visitBlock(LambdaToMethod.java:1312)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1092)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitMethodDef(TreeTranslator.java:150)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.visitMethodDef(LambdaToMethod.java:1445)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:916)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:70)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitClassDef(TreeTranslator.java:139)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.visitClassDef(LambdaToMethod.java:1354)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:814)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:70)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitClassDef(TreeTranslator.java:139)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.visitClassDef(LambdaToMethod.java:1354)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:814)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod$LambdaAnalyzerPreprocessor.analyzeAndPreprocessClass(LambdaToMethod.java:1278)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod.visitClassDef(LambdaToMethod.java:302)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:814)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod.translate(LambdaToMethod.java:267)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod.translate(LambdaToMethod.java:260)
at jdk.compiler/com.sun.tools.javac.comp.LambdaToMethod.translateTopLevelClass(LambdaToMethod.java:287)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1642)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1475)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:976)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:319)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:178)
at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:66)
at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:52)